In-plane switching LCD panel

ABSTRACT

The present invention discloses an array substrate for an IPS-LCD device. The IPS-LCD device according to the present invention implements a multi-domain for a liquid crystal layer. The liquid crystal molecules are aligned in various directions with respect to each different domain. Therefore, the different domains compensate for one another such that a color shift is prevented in spite of wide viewing angles. To form the multi-domain, the present invention provides an array substrate having divided common electrode or pixel electrode or both. In another aspect, to form the multi-domain, the present invention provides an array substrate having multi-bar shaped common and pixel electrodes. Each of the common and pixel electrodes has a transverse portion and a perpendicular portion. The transverse portions of the common and pixel electrodes induce a first domain, whereas the perpendicular potions of the common and pixel electrodes induce a second domain.

This application is a Divisional application Ser. No. 10/620,575, filedon Jul. 17, 2003, now U.S. Pat. No. 7,057,696, which is a Divisional ofApplication Ser. No. 09/836,352, filed Apr. 18, 2001, now U.S. Pat. No.6,636,289, which claims priority to Korean Application Nos. 2000-20722and 2000-45988, filed Apr. 19, 2000 and Aug. 8, 2000 respectively, allof which are hereby incorporated by reference as if fully set forthherein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a liquid crystal display device, andmore particularly to a liquid crystal display device implementingin-plane switching (IPS) where an electric field to be applied to liquidcrystal is generated in a plane parallel to a substrate.

2. Discussion of the Related Art

A typical liquid crystal display (LCD) device uses optical anisotropyand polarization properties of liquid crystal molecules. The liquidcrystal molecules have a definite orientational order in alignmentresulting from their thin and long shapes. The alignment orientation ofthe liquid crystal molecules can be controlled by supplying an electricfield to the liquid crystal molecules. In other words, as the alignmentdirection of the electric field is changed, the alignment of the liquidcrystal molecules also changes. Because incident light is refracted tothe orientation of the liquid crystal molecules due to the opticalanisotropy of the aligned liquid crystal molecules, image data isdisplayed.

A liquid crystal is classified into a positive liquid crystal and anegative liquid crystal, in view of electrical property. The positiveliquid crystal has a positive dielectric anisotropy such that long axesof liquid crystal molecules are aligned parallel to an electric field.Whereas, the negative liquid crystal has a negative dielectricanisotropy such that long axes of liquid crystal molecules are alignedperpendicular to an electric field.

By now, an active matrix LCD that the thin film transistors and thepixel electrodes are arranged in the form of a matrix is mostattention-getting due to its high resolution and superiority indisplaying moving video data.

FIG. 1 is a cross-sectional view illustrating a typical twisted nematic(TN) LCD panel. As shown in FIG. 1, the TN-LCD panel has lower and uppersubstrates 2 and 4 and an interposed liquid crystal layer 10. The lowersubstrate 2 includes a first transparent substrate 1 a and a thin filmtransistor (“TFT”) “S”. The TFT “S” is used as a switching element tochange orientation of the liquid crystal molecules. The lower substrate2 further includes a pixel electrode 15 that applies an electric fieldto the liquid crystal layer 10 in accordance with signals applied by theTFT “S”. The upper substrate 4 has a second transparent substrate 1 b, acolor filter 8 on the second transparent substrate 4, and a commonelectrode 14 on the color filter 8. The color filter 8 implements colorfor the LCD panel. The common electrode 14 serves as another electrodefor applying a voltage to the liquid crystal layer 10. The pixelelectrode 15 is arranged over a pixel portion “P,” i.e., a display area.Further, to prevent leakage of the liquid crystal layer 10 between thelower and upper substrates 2 and 4, those substrates are sealed by asealant 6.

As described above, because the pixel and common electrodes 15 and 14 ofthe conventional TN-LCD panel are positioned on the lower and uppersubstrates 2 and 4, respectively, the electric field inducedtherebetween is perpendicular to the lower and upper substrates 1 a and1 b. The above-mentioned liquid crystal display device has advantages ofhigh transmittance and aperture ratio, and further, since the commonelectrode on the upper substrate serves as an electrical ground, theliquid crystal is protected from a static electricity.

FIGS. 2A and 2B show different alignments of the positive TN liquidcrystal molecules 10, respectively, without and with an electric field(off and on states). In FIG. 2A, various arrows show the gradualrotating of the liquid crystal molecules 10 with polar angles 0 to 90degrees, which are measured on a plane parallel to the lower and uppersubstrate 2 and 4. At the same time, the liquid crystal molecules 10 aregradually rotated to 90 degrees from the lower substrate 2 to the uppersubstrate 4. That is to say, the long axes of the liquid crystalmolecules 10 gradually rotate along a helical axis (not shown) that isperpendicular to the lower and upper substrates 2 and 4. First andsecond polarizers 18 and 30 are positioned, respectively, on theexterior surfaces of the lower and upper substrates. Referring to FIG.2A, the broken lines on the first and second polarizers 18 and 30correspond to first and second transmittance axis of the first andsecond polarizers 18 and 30, respectively. After rays of light travelthrough a TN liquid crystal panel in the off state, as described above,they are linearly polarized and rotated 90 degrees.

As shown in FIG. 2B, when there is an electric field “E” applied to thepositive TN liquid crystal molecules 10, the liquid crystal moleculesare aligned perpendicular to the upper and lower substrates 4 and 2.That is to say, with the electric field “E” applied across the liquidcrystal molecules 10, the liquid crystal molecules 10 rotate to beparallel to the electric field “E”. In this case, the rotation of thelinearly polarized light does not take place. Therefore, light isblocked by the second polarizers 30 after it travels through the firstpolarizer 18.

However, the above-mentioned operation mode of the TN-LCD panel has adisadvantage of a narrow viewing angle. That is to say, the TN liquidcrystal molecules rotate with polar angles 0 to 90 degrees, which aretoo wide. Because of the large rotating angle, contrast ratio andbrightness of the TN-LCD panel fluctuate rapidly with respect to theviewing angles.

To overcome the above-mentioned problem, an in-plane switching (IPS) LCDpanel was developed. The IPS-LCD panel implements a parallel electricfield that is parallel to the substrates, which is different from the TNor STN (super twisted nematic) LCD panel. A detailed explanation aboutoperation modes of a typical IPS-LCD panel will be provided withreference to FIGS. 3, 4A, and 4B.

As shown in FIG. 3, first and second substrates 1 a and 1 b are spacedapart from each other, and a liquid crystal “LC” is interposedtherebetween. The first and second substrates 1 a and 1 b are called anarray substrate and a color filter substrate, respectively. Pixel andcommon electrodes 15 and 14 are disposed on the first substrate 1 a. Thepixel and common electrodes 15 and 14 are parallel with and spaced apartfrom each other. On a surface of the second substrate 1 b, a colorfilter 25 is disposed opposing the first substrate 1 a. The pixel andcommon electrodes 15 and 14 apply an electric field “E” to the liquidcrystal “LC”. The liquid crystal “LC” has a negative dielectricanisotropy, and thus it is aligned parallel to the electric field “E”.

FIGS. 4A and 4B conceptually illustrate operation modes for a typicalIPS-LCD device. In an off state, the long axes of the LC molecules “LC”maintain a definite angle with respect to a line that is perpendicularto the pixel and common electrodes 15 and 14. The pixel and commonelectrode 15 and 14 are parallel with each other. Herein, the angledifference is 45 degrees, for example.

In an on state, an in-plane electric field “E”, which is parallel withthe surface of the first substrate 1 a, is generated between the pixeland common electrodes 15 and 14. The reason is that the pixel electrode15 and common electrode 14 are formed together on the first substrate 1a. Then, the LC molecules “LC” are twisted such that the long axesthereof coincide with the electric field direction. Thereby, the LCmolecules “LC” are aligned such that the long axes thereof areperpendicular to the pixel and common electrodes 15 and 14.

In the above-mentioned IPS-LCD panel, there is no transparent electrodeon the color filter, and the liquid crystal used in the IPS-LCD panelincludes a negative dielectric anisotropy.

FIGS. 5A and 5B are conceptual plane views illustrating alignment of theliquid crystal molecules of the above-mentioned IPS-LCD panel,respectively, in off and on states. As shown in FIG. 5A, each liquidcrystal molecule 10 is aligned in a proper direction by a pair ofalignment layers (not shown), which are formed on opposing surfaces ofthe first and second substrate 1 a and 1 b. As shown in FIG. 5B, theelectric field “E” is applied between the pixel and common electrodes 15and 14 such that each molecule 10 is aligned in accordance with theelectric field “E”. That is to say, each liquid crystal molecule 10rotates to a definite angle in accordance with the electric field “E”.

Compared with the TN-LCD device of FIG. 1, the IPS-LCD device has awider viewing angle owing to a smaller rotating angle of the liquidcrystal molecules.

The IPS-LCD device has the advantage of a wide viewing angle. Namely,when a user looks at the IPS-LCD device in a top view, the wide viewingangle of about 70 degrees is achieved in up, down, right and leftdirections.

By the above-mentioned operation modes and with additional elements suchas polarizers and alignment layers, the IPS-LCD device displays images.The IPS-LCD device has a wide viewing angle, low color dispersionqualities, and the fabricating processes thereof are simpler among thoseof various LCD devices.

However, because the pixel and common electrodes are disposed on thesame plane on the lower substrate, the transmittance and aperture ratioare low. In addition, a response time according to a driving voltageshould be improved, and a color's dependence on the viewing angle shouldbe decreased.

FIG. 6 is a graph of the CIE (Commission Internationale de l'Eclairage)color coordinates and shows the color dispersion property of theconventional IPS-LCD device. The horseshoe-shaped area is thedistribution range of the wavelength of visible light. The results aremeasured using point (0.313, 0.329) in CIE coordinate as a standardwhite light source and with various viewing angles of right, left, upand down, and 45 and 135 degrees. Obviously, the range of the colordispersion is so long, which means that the white light emitted from theconventional IPS-LCD device is dispersed largely according to theviewing angle. This results from the fact that the operation mode of theIPS-LCD device is controlled by birefringence. S. Endow et al. indicatedthe above-mentioned problem in their paper “Advanced 18.1-inch DiagonalSuper-TFT-LCDs with Mega Wide Viewing Angle and Fast Response Speed of20 ms: IDW 99' 187 page”.

FIG. 7 is a graph illustrating transmittance with respect to viewingangles for first to eighth gray levels (gray scale) of a conventionalIPS-LCD device. Except for the first gray level, “level 1,” each graylevel has the highest transmittance at a viewing angle of 0 degree. Thefirst gray level, “level 1” has gray inversion regions. When the viewingangle is beyond 60 degrees, the first gray level, “level 1,” has thehigher transmittance than the fourth gray level, “level 4”. The firstgray level, “level 1,” should implement a black state of the LCD panel.However, gray inversion occurs at viewing angles larger than 60 degrees,such that a white state, but not a black state, is produced at thelarger viewing angles. The above-mentioned gray inversion results from abirefringence dependence of the IPS-LCD device and causes poor displayquality of the IPS-LCD device.

To achieve the wide viewing angle and an improved color dispersionproperty, the common and pixel electrodes for the IPS-LCD device aredesigned to have various shapes. FIG. 8 illustrates a first example ofthe IPS-LCD device according to a related art. As shown in FIG. 8, aplurality of pixel and common electrode 15 and 14 are alternatelyarranged on a substrate (reference 1 a of FIG. 3) having a thin filmtransistor “S”. At this point, an alignment layer (not shown) is formedon the substrate (not shown). The alignment layer has first and secondrubbing directions 40 a and 40 b, respectively, in accordance with firstand second domains “A” and “B” such that a multi-domain for liquidcrystal molecules 10 is achieved.

Therefore, the liquid crystal molecules 10 are divided into first andsecond liquid crystal portions 10 a and 10 b, which correspond to thefirst and second domains “A” and “B”, respectively. In accordance withthe first and second rubbing directions 40 a and 40 b, the first andsecond liquid crystal portions 10 a and 10 b are aligned to havesymmetric pretilt angles. The above-mentioned multi-domain hasadvantages of preventing color filter shift and achieving the wideviewing angle.

FIGS. 9A and 9B, respectively, show expanded views of the first andsecond domains “A” and “B” of FIG. 8. In the off state, the first andsecond liquid crystal portions 10 a and 10 b (broken lines) are alignedin accordance with the first and second rubbing directions 40 a and 40b, respectively.

Therefore, the first and second liquid crystal portions 10 a and 10 bare respectively aligned to have symmetric pretilt angles. Whereas, whenan electric field “E” is applied between the pixel and common electrodes15 and 14, the first and second liquid crystal portions 10 a and 10 b(continuous lines) are aligned in accordance with the electric field“E”. Therefore, the first and second liquid crystal portions 10 a and 10b are aligned in the same direction. In other words, a single-domain ispresent for the on state, or the white state.

The above-mentioned single-domain of the on state causes a narrowviewing angle and a color shift. For example, instead of white, yellowis displayed when a user watches along short axes of the liquid crystalmolecules, and blue is displayed when the user watches along long axesof the liquid crystal molecules.

FIG. 10 shows a second example of the IPS-LCD device according to therelated art. As shown, zigzag-shaped pixel electrodes 35 andzigzag-shaped common electrodes 34 are alternately arranged such thatfirst and second electric fields 46 a and 46 b are alternately inducedalong the zigzag-shaped electrodes. The first and second electric fields46 a and 46 b have different directions. Therefore, a multi-domain isachieved owing to the first and second electric fields 46 a and 46 b. Analignment layer (not shown) is also used for a first state alignment ofliquid crystal molecules (reference 10 of FIG. 8). The alignment layer(not shown) beneficially has one rubbing direction 60 instead of thefirst and second rubbing directions 40 a and 40 b of FIG. 8. Incomparison with the first example shown in FIG. 8, many more domains areproduced by the second example.

The above-mentioned zigzag-shaped common and pixel electrodes 34 and 35minimize the color shift. However, between bending portions “D” of thecommon and pixel electrodes 34 and 35, an electric field is inducedperpendicular to the rubbing direction 44. That is to say, long axes ofthe liquid crystal molecules are perpendicular to the electric fieldinduced between the bending portions “D”. Then, the liquid crystalmolecules cannot rotate but keep the first state alignment such that anabnormal alignment is present at each boundary portion “C” between thedifferent domains.

The abnormal alignment at the boundary portion “C” causes a light leaksuch that white lines are shown on a display area, the pixel region “P”shown in FIG. 1, of the LCD device. The above-mentioned white lines arecalled a disclination. A black matrix may be expanded to the pixelregions to cover the disclination. However, the expanded black matrixcauses a low aperture ratio.

Now, with reference to FIGS. 11A and 11B, effect of the multi-domain isexplained in detail. A liquid crystal layer generally has abirefringence, because each liquid crystal molecule has a long and thinshape. The birefringence changes with respect to a viewing angle. FIG.11A is a cross-sectional view illustrating a single-domain for a liquidcrystal molecule 10 between upper and lower polarizers 30 and 18. Atthis point, the birefringence of the liquid crystal molecule 10 involvesdifferent values for the first, second, and third position “a”, “b”, and“c”, which involve different viewing angles. Therefore, thebirefringence of the liquid crystal molecule 10 cannot be zero withrespect to viewing angles. If the birefringence of the liquid crystallayer is not zero, the perfect black state cannot be achieved betweenthe upper and lower polarizers 30 and 18.

To overcome the above-mentioned problem, the multi-domain shown in FIG.11B is adopted for a LCD device. As shown, there are first and secondliquid crystal molecules 10 a and 10 b arranged opposite to each other.The birefringence of the first liquid crystal molecule 10 a involvesdifferent values for the first, second, and third position “a₁”, “b₁”,and “c₁”. Whereas, the birefringence of the second liquid crystalmolecule 10 b involves different values for the fourth, fifth, and sixthposition “a₂”, “b₂”, and “c₂”. The first and fourth positions “a₁” and“a₂” involve the same viewing angle. Because the first and second liquidcrystal molecules 10 a and 10 b are symmetrically opposed with eachother, a birefringence of the first liquid crystal molecule 10 a at thefirst position “a₁” is compensated by that of the second liquid crystalmolecule 10 b at the fourth position “b₂”. That is to say, eachbirefringence of the first liquid crystal molecule 10 a is compensatedby corresponding birefringence of the second liquid crystal molecule 10b. In other words, sum of the birefringence between the first and secondliquid crystal molecules 10 a and 10 b is about zero. Accordingly, themulti-domain shown in FIG. 11B improves the display quality of the LCDdevice.

SUMMARY OF THE INVENTION

Accordingly, the present invention is directed to an IPS-LCD device thatsubstantially obviates one or more of the problems due to limitationsand disadvantages of the related art.

An object of the present invention is to provide an IPS-LCD devicehaving low color dispersion and low white inversion with respect toviewing angles.

Another object of the present invention is to provide an IPS-LCD devicehaving optimized common and pixel electrodes such that high apertureratio, low color shift, and fast response time are achieved.

Additional features and advantages of the invention will be set forth inthe description which follows, and in part will be apparent from thedescription, or may be learned by practice of the invention. Theobjectives and other advantages of the invention will be realized andattained by the structure particularly pointed out in the writtendescription and claims hereof as well as the appended drawings.

In order to achieve the above object, the first preferred embodiment ofthe present invention provides an array substrate for an IPS-LCD device.The array substrate includes: a substrate; a gate line on the substrate;a data line perpendicular to the gate line; a thin film transistor at acrossing portion between the gate and data lines; a common line parallelto the gate line; a plurality of common electrodes perpendicular to thecommon line, wherein the common electrodes are spaced apart from eachother and at least one of the common electrodes is divided into firstand second portions that are co-linear and separated by a predetermineddistance; and a plurality of pixel electrodes parallel to the pluralityof common electrodes, wherein the plurality of pixel and commonelectrodes are alternately arranged such that the array substrate isused for the IPS-LCD device.

The first and second portions of the common electrode are about equal inlength such that first and second domains for a liquid crystal areproduced by the array substrate. Beneficially, the pixel electrodeadjacent the first and second portions of the common electrode includesa male electrode opposing a boundary between the first and secondportions of the common electrode.

At least one of the pixel electrodes is divided into first and secondportions that are co-linear and spaced apart by a predetermineddistance. The second portions of the common and pixel electrodes areabout twice as long as the first portions of, respectively, the commonand pixel electrodes, the first portion of the common electrode opposesthe second portion of the pixel electrode, and the second portion of thecommon electrode opposes the first portion of the pixel electrode.Beneficially, the common electrode adjacent the pixel electrode includesa male electrode that opposes a boundary between the first and secondportions of the pixel electrode. In addition, the pixel electrodeadjacent the common electrode beneficially includes a male electrodethat opposes a boundary between the first and second portions of thecommon electrode.

The pixel electrode is selected from a group consisting of indium tinoxide (ITO) and indium zinc oxide (IZO). The common electrode isselected from a group consisting of chromium (Cr), aluminum (Al),aluminum alloy (Al alloy), molybdenum (Mo), tantalum (Ta), tungsten (W),antimony (Sb), and an alloy thereof, or is beneficially selected from agroup consisting of indium tin oxide (ITO) and indium zinc oxide (IZO).

In another aspect, the present invention provides an array substrate foran IPS-LCD device. The array substrate includes: a substrate; a gateline on the substrate; a data line perpendicular to the gate line; athin film transistor at a crossing portion between the gate and datalines; a main common line parallel to the gate line; first and secondauxiliary common lines perpendicular to the main common line, the firstand second auxiliary common lines being parallel to and spaced apartfrom each other; a plurality of common electrodes perpendicular to thefirst and second auxiliary common lines, wherein the common electrodesbeing spaced apart from each other and at least one of the commonelectrodes is divided into first and second portions that are co-linearand separated by a predetermined distance; and a plurality of pixelelectrodes parallel to the plurality of common electrodes, wherein theplurality of pixel and common electrodes are alternately arranged suchthat the array substrate is used for the IPS-LCD device.

The first and second portions are about equal in length such that firstand second domains for a liquid crystal are produced by the arraysubstrate. Beneficially, the pixel electrode adjacent the first andsecond portions of the common electrode includes a male electrode thatopposes an boundary between the first and second portions.

At least one of the pixel electrodes is divided into first and secondportions that are co-linear and separated by a predetermined distance.The second portions of the common and pixel electrodes are about twiceas long as the first portions of, respectively, the common and pixelelectrodes, the first portion of the common electrode opposes the secondportion of the pixel electrode, and the second portion of the commonelectrode opposes the first portion of the pixel electrode.

The common electrode adjacent the pixel electrode includes a maleelectrode that opposes a boundary between the first and second portionsof the pixel electrode. The pixel electrode adjacent the commonelectrode includes a male electrode that opposes a boundary between thefirst and second portions of the common electrode.

In another aspect, the present invention provides an array substrate foran IPS-LCD device. The array substrate includes: a substrate; a gateline on the substrate; a data line perpendicular to the gate line; athin film transistor at a crossing portion between the gate and datalines; a common line parallel to the gate line; a plurality of commonelectrodes extending perpendicular to the common line; a plurality ofpixel electrodes arranged alternately with the plurality of commonelectrodes; an auxiliary common electrode perpendicularly contactingeach of the common electrodes; and an auxiliary pixel electrodeperpendicularly contacting each of the pixel electrodes, wherein theauxiliary pixel electrodes is spaced apart from the auxiliary commonelectrode and wherein the plurality of common electrodes and theplurality of pixel electrodes are on a same layer.

In another aspect, the present invention provides an array substrate foran IPS-LCD device. The array substrate includes: a substrate; a gateline on the substrate; a data line perpendicular to the gate line; athin film transistor at a crossing portion between the gate and datalines; a common line parallel to the gate line, the common lineincluding first and second auxiliary common lines perpendicular to thecommon line; a plurality of common electrodes extending perpendicular tothe first and second auxiliary common lines; a plurality of pixelelectrodes arranged alternately with the plurality of common electrodes;an auxiliary common electrode perpendicularly contacting each of thecommon electrodes; and an auxiliary pixel electrode perpendicularlycontacting each of the pixel electrodes, wherein the auxiliary pixelelectrodes is spaced apart from the auxiliary common electrode.

In another aspect, the present invention provides an array substrate foran IPS-LCD device. The array substrate includes; a substrate; a gateline on the substrate; a data line perpendicular to the gate line; athin film transistor at a crossing portion between the gate and datalines; a common line parallel to the gate line, the common lineincluding a plurality of common electrodes extending perpendicular tothe common line; a plurality of pixel electrodes arranged alternatelywith the plurality of common electrodes; a plurality of auxiliaryelectrodes connecting the plurality of common and pixel electrodes in acheck pattern.

In another aspect, the present invention provides an array substrate foran IPS-LCD device. The array substrate includes; a substrate; a gateline on the substrate; a data line perpendicular to the gate line; athin film transistor at a crossing portion between the gate and datalines; a pixel region surrounded by the gate and data lines, the pixelregion including first and second domains; a transparent pixel electrodeincluding (a) first and second perpendicular pixel electrodes, (b) aplurality of first transverse pixel electrodes, and (c) a secondtransverse pixel electrode, wherein the first perpendicular pixelelectrode is disposed along the first and second domains andperpendicular to the gate line, the second perpendicular pixel electrodeis disposed on the second domain and parallel to the first perpendicularpixel electrode, the plurality of first transverse pixel electrodesperpendicularly extends from the first perpendicular pixel electrode onthe first domain, and the second transverse pixel electrode connects thefirst and second perpendicular pixel electrodes on the second domain; acommon line parallel to the gate line; and a common electrode including(a) first to third perpendicular common electrodes, (b) a plurality offirst transverse common electrodes, and (c) a second transverse commonelectrode, wherein the first and second perpendicular common electrodeis disposed along the first and second domains and parallel to the firstand second perpendicular pixel electrodes, the third perpendicularcommon electrode is disposed on the second domain and between the firstand second perpendicular common electrodes, the plurality of firsttransverse common electrodes are alternately arranged with the pluralityof transverse pixel electrodes on the first domain, and the secondtransverse common electrode connects the first to third perpendicularcommon electrodes.

An outermost first transverse pixel electrode overlaps a portion of thegate line. The common electrode is a transparent conductive material.

The array substrate further includes an alignment layer having first andsecond rubbing directions, which correspond to the first and seconddomains, respectively.

In another aspect, the present invention provides a method forfabricating an array substrate of an IPS-LCD device. The methodincludes: preparing a substrate; forming a gate line including a gateelectrode on the substrate; forming a gate-insulating layer on thesubstrate such that the gate-insulating layer covers the gate line andgate electrode; forming an active layer and ohmic contact layer on thegate-insulating layer; forming a data line including a source electrode,and a drain electrode on the gate-insulating layer; forming a firstpassivation layer on the gate-insulating layer such that the firstpassivation layer covers the data line, source electrode, and drainelectrode, the gate-insulating layer having a drain contact hole overthe drain electrode; forming a pixel electrode on the first passivationlayer, the pixel electrode including (a) first and second perpendicularpixel electrodes, (b) a plurality of first transverse pixel electrodes,and (c) a second transverse pixel electrode, wherein the firstperpendicular pixel electrode is disposed along the first and seconddomains and perpendicular to the gate line, the second perpendicularpixel electrode is disposed on the second domain and parallel to thefirst perpendicular pixel electrode, the plurality of first transversepixel electrodes perpendicularly extends from the first perpendicularpixel electrode on the first domain, and the second transverse pixelelectrode connects the first and second perpendicular pixel electrodeson the second domain; forming a second passivation layer on the pixelelectrode; forming a common lines including a common electrode on thesecond passivation layer, the common electrode including (a) first tothird perpendicular common electrodes, (b) a plurality of firsttransverse common electrodes, (c) and a second transverse commonelectrode, wherein the first and second perpendicular common electrodeis disposed along the first and second domains and parallel to the firstand second perpendicular pixel electrodes, the third perpendicularcommon electrode is disposed on the second domain and between the firstand second perpendicular common electrodes, the plurality of firsttransverse common electrodes are alternately arranged with the pluralityof transverse pixel electrodes on the first domain, and the secondtransverse common electrode connects the first to third perpendicularcommon electrodes; and forming an alignment layer on the commonelectrode, the alignment layer having first and second rubbingdirections.

The method further includes the step of forming a planar layer on thecommon electrode before forming the alignment layer.

An outermost first transverse pixel electrode overlaps a portion of thegate line. The common electrode is a transparent conductive material.

The first and second rubbing directions are symmetrical with respect toa line parallel to the gate line.

In another aspect, the present invention provides an array substrate foran LCD-device. The array substrate includes: a substrate; a gate line onthe substrate; a data line perpendicular to the gate line; a thin filmtransistor at a crossing portion between the gate and data lines; apixel region surrounded by the gate and data lines, the pixel regionincluding first and second domains; transverse pixel and commonelectrodes disposed on the first domain and parallel to the gate line,the transverse pixel and common electrodes being alternately arranged;perpendicular pixel and common electrodes disposed on the second domainand perpendicular to the transverse pixel and common electrodes,respectively, the perpendicular pixel and common electrodes beingalternately arranged; and an alignment layer having first and secondrubbing directions, the first and second rubbing directionscorresponding to the first and second domains, respectively.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory and areintended to provide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWING

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification, illustrate embodiments of the invention andtogether with the description serve to explain the principles of theinvention.

In the drawings:

FIG. 1 is a cross-sectional view illustrating a typical liquid crystaldisplay device;

FIGS. 2A and 2B illustrate operation modes of a typical TN-LCD panel;

FIG. 3 is a cross-sectional view illustrating a typical IPS-LCD device;

FIGS. 4A and 4B are perspective views illustrating operation modes ofthe typical IPS-LCD device of FIG. 3;

FIGS. 5A and 5B are plan views illustrating, respectively, off statealignment and on state alignment of liquid crystal molecules of theIPS-LCD device shown in FIG. 3;

FIG. 6 is a CIE graph illustrating a color coordinate property withrespect to various viewing angles of the typical IPS-LCD device;

FIG. 7 is a graph illustrating transmittance with respect to viewingangles for first to eighth gray levels of the typical IPS-LCD device;

FIG. 8 is a plan view illustrating the first example for an IPS-LCDdevice according to the related art;

FIGS. 9A and 9B are expanded plan views illustrating, respectively,first and second domains “A” and “B” of FIG. 8;

FIG. 10 is a plan view illustrating the second example for an IPS-LCDdevice according to the related art;

FIGS. 11A and 11B are cross-sectional views illustrating, respectively,single-domain and multi-domain for liquid crystal molecules;

FIG. 12 is a plan view illustrating an IPS-LCD device according to thefirst preferred embodiment of the present invention;

FIG. 13 is an expanded plan view of a portion “Z” of FIG. 12;

FIG. 14 is a plan view illustrating a degree of freedom for a liquidcrystal molecule according to the preferred embodiment;

FIG. 15 is a plan view illustrating an IPS-LCD device according to thesecond preferred embodiment of the present invention;

FIG. 16 is a plan view illustrating an IPS-LCD device according to thethird preferred embodiment of the present invention;

FIG. 17 is an expanded plan view of a portion “J” of FIG. 16;

FIG. 18 is a plan view illustrating an IPS-LCD device according to thefourth preferred embodiment of the present invention;

FIGS. 19 and 20 are plan views illustrating modifications of an IPS-LCDdevice according to the fifth preferred embodiment of the presentinvention;

FIGS. 21 and 22 are plan views illustrating modifications of an IPS-LCDdevice according to the sixth preferred embodiment of the presentinvention;

FIG. 23 is a plan view illustrating an IPS-LCD device according to theseventh preferred embodiment of the present invention;

FIG. 24A is a plan view illustrating an IPS-LCD device according to theeighth preferred embodiment of the present invention;

FIG. 24B is a plan view illustrating a principle of the eight preferredembodiment of FIG. 24A; and

FIGS. 25A, 25B, 26A, 26B, 27A, and 27B are sequential cross-sectionalviews illustrating a fabricating method for the IPS-LCD device of FIG.24A.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference will now be made in detail to the preferred embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings.

First Preferred Embodiment

FIG. 12 is a plan view illustrating a pixel region of an IPS-LCD deviceaccording to the first preferred embodiment. As shown, a gate line 50and a common line 60 are transversely arranged, and a data line 70 isformed perpendicular to the gate and common lines. A plurality of pixelelectrodes 76 are formed perpendicular to the gate and common lines 50and 60. At a crossing point between the gate and data lines 50 and 70, agate electrode 52 and a source electrode 72 are integrally formed withthe gate and data lines 50 and 70, respectively. In addition, a drainelectrode 74 is formed spaced apart from the source electrode 72. Thegate, source, and drain electrodes 52, 72, and 74 are included in a thinfilm transistor “S”.

The common line 60 includes a plurality of common electrodes 62. Thecommon electrodes 62 are perpendicular to the common line 60 andparallel with each other. At this point, each common electrode 62 is cutinto first and second portions 62 a and 62 b, which are co-linear, witha boundary line “X” therebetween. The first and second portions 62 a and62 b involve different domains for a liquid crystal layer (reference 10of FIG. 1), which will be explained in detail with reference to FIG. 13.The common electrodes 62 and pixel electrodes 76 are alternatelyarranged.

FIG. 13 is an expanded plan view of a portion “Z” of FIG. 12. A firstdomain “M1” and a second domain “M2” for liquid crystal molecules 80 arecentered on the boundary line “X” and symmetrically formed. The firstdomain “M1” is defined by a first electric field “E1” induced betweenthe first portion 62 a of the common electrode 62 and the adjacent pixelelectrode 76. Whereas, the second domain “M2” is defined by a secondelectric field “E2” induced between the second portion 62 b of thecommon electrode 62 and the adjacent pixel electrode 76. At this point,each of the first and second electric fields “E1” and “E2” is distortedin opposite directions near the boundary line “X”. Then, the liquidcrystal molecules 80 are aligned in first and second directionscorresponding to the first and second electric fields “E1” and “E2”,respectively, such that the first and second domains “M1” and “M2” haveopposite alignment directions. The first and second electric fields “E1”and “E2” have a characteristic of a fringe field.

Preferably, the liquid crystal molecules 80 are a positive liquidcrystal having positive dielectric anisotropy. In addition, in the offstate, long axes of the liquid crystal molecules 80 are preferablyaligned parallel to the common and pixel electrodes 62 and 76. That isto say, a rubbing direction of an alignment layer (not shown) for theliquid crystal molecules 80 is preferably parallel to the common andpixel electrodes 62 and 76.

FIG. 14 shows a degree of freedom for liquid crystal molecule 80 withrespect to a rubbing direction 100. In a first state alignment (offstate), the liquid crystal molecule 80 is aligned corresponding to therubbing direction 100, which is preferably parallel to the common andpixel electrodes 62 and 76 of FIG. 12. As shown, the liquid crystalmolecule 80 can rotate right or left, which means that the degree offreedom of the liquid crystal molecule 80 is two. Therefore, the firstelectric field “E1” or second electric fields “E2” of FIG. 13 can causethe liquid crystal molecule 80 to rotate left or right such that thefirst and second domains “M1” and “M2” are formed.

The liquid crystal molecules 80 may be negative liquid crystal insteadof the positive liquid crystal. In that case, the rubbing direction 100is preferably perpendicular to the common electrodes 62 and pixelelectrodes 76.

The above-mentioned multi-domain decreases a color's dependence onviewing angles such that a gray inversion shown in FIG. 7 is prevented.

Second Preferred Embodiment

FIG. 15 is a plan view illustrating a pixel region of an IPS-LCD deviceaccording to the second preferred embodiment. As shown, a gate line 50and a common line 60 are transversely arranged, and a data line 70 isformed perpendicular to the gate and common lines 50 and 60. A pluralityof pixel electrodes 86 are formed parallel to the gate and common lines50 and 60. A thin film transistor “S” is disposed at a crossing pointbetween the gate and data lines 50 and 70.

The common line 60 has first and second auxiliary common lines 181 a and181 b, which are perpendicular to the common line 60 and spaced apartfrom each other. In addition, a plurality of common electrodes 82 areformed perpendicular to the first and second auxiliary common lines 181a and 181 b. The common electrodes 82 and pixel electrodes 86 arealternately arranged. At this point, each common electrode 82 is cutinto first and second portions 82 a and 82 b, which are co-linear, witha boundary line “Y” centered on therebetween.

Compared with the first preferred embodiment shown in FIG. 14, thesecond preferred embodiment adopts the common and pixel electrodes 82and 86 that are parallel to the common and gate lines 60 and 50, insteadof being perpendicular thereto. Therefore, first and second domains “M1”and “M2” are symmetrically formed on the left and right of the boundaryline “Y”. Since the first and second domains “M1” and “M2” have the samecharacteristic as shown in FIG. 13, additional description is omitted.

A positive liquid crystal (reference 80 of FIG. 13) is preferably usedwith a rubbing direction that is parallel to the common and pixelelectrodes 82 and 86. If a negative liquid crystal is used for thesecond preferred embodiment, a rubbing direction that is perpendicularto the common and pixel electrodes 82 and 86 is employed for the secondpreferred embodiment.

Third Preferred Embodiment

FIG. 16 is a plan view illustrating a pixel region of an IPS-LCD deviceaccording to the third preferred embodiment. Compared with the firstpreferred embodiment of FIG. 13, the third preferred embodiment providesfirst, second, and third domains “M1,” “M2,” and “M3.” Except for commonand pixel electrodes 64 and 78, all the elements have the same structureas the first preferred embodiment of FIG. 13. The pixel region(reference “P” of FIG. 1) is an area defined by gate and data lines 50and 70.

As shown in FIG. 16, a common line 60 has a plurality of commonelectrodes 64, which are spaced apart from each other. Each commonelectrode 64 is divided into co-linear first and second commonsub-electrodes 64 a and 64 b with a first boundary line “X1” such thatthe second common sub-electrode 64 b is preferably twice as long as thefirst common sub-electrode 64 a. In addition, a plurality of the pixelelectrodes 78 are alternately arranged with the common electrodes 64.Each pixel electrode 78 is also divided into co-linear first and secondpixel sub-electrodes 78 a and 78 b with a second boundary line “X2” suchthat the second pixel sub-electrode 78 b is twice as long as the firstpixel sub-electrode 78 a. That is to say, the first and second boundarylines “X1” and “X2” divide the pixel region into the first, second, andthird domains “M1,” “M2,” and “M3.”

FIG. 17 is an expanded plan view of a portion “J” of FIG. 16. As shown,each of the first to third domains “M1” to “M3” has a differentalignment for liquid crystal molecules 80. Compared with the firstpreferred embodiment of FIG. 13, each domain of the second preferredembodiment is shorter than that of the first preferred embodiment. Atthis point, between the common and pixel electrodes 64 and 78, variousfringe fields are induced. A fringe field effect is stronger when moredomains are present on the same region. That is to say, the secondpreferred embodiment has the stronger electric field than the firstpreferred embodiment such that restoring force against an exteriorelectric impact (electric field or the like) is stronger for the secondpreferred embodiment. Therefore, the liquid crystal molecules 80 have afaster response time such that they restore to a first state alignmentmore quickly when the electric field is stopped.

Preferably, the liquid crystal molecules 80 are a positive liquidcrystal having positive dielectric anisotropy. In that case, a rubbingdirection of an alignment layer (not shown) for the liquid crystalmolecules 80 is preferably parallel to the common and pixel electrodes64 and 78. On the contrary, the liquid crystal molecules 80 may benegative liquid crystal instead of the positive liquid crystal. In thatcase, the rubbing direction 100 is preferably perpendicular to thecommon electrodes 62 and pixel electrodes 76.

Fourth Preferred Embodiment

For the fourth preferred embodiment, common and pixel electrodes areformed parallel to the common and gate lines. As shown in FIG. 18, agate line 50 and a common line 60 are transversely arranged, and a dataline 70 is formed perpendicular to the gate and common lines. Aplurality of pixel electrodes 88 are formed parallel to the gate andcommon lines 50 and 60. Each pixel electrode 88 is divided into firstand second pixel sub-electrodes 88 a and 88 b.

The common line 60 has first and second auxiliary common lines 180 a and180 b, which are perpendicular to the common line 60 and spaced apartfrom each other. In addition, a plurality of common electrodes 84 areformed perpendicular to the first and second auxiliary common lines 180a and 180 b. The common electrodes 84 and pixel electrodes 88 arealternately arranged. At this point, each common electrode 84 is dividedinto co-linear first and second common sub-electrodes 84 a and 84 b witha first boundary line “Y1” dividing them. The first common sub-electrode84 a is preferably half the length of the second common sub-electrode 84b. In addition, each pixel electrode 88 is divided into co-linear firstand second pixel sub-electrodes 88 a and 88 b with a second boundaryline “Y2” dividing them. The first pixel sub-electrode 88 a ispreferably half the length of the second pixel sub-electrode 88 b. Thatis to say, the fourth preferred embodiment provides first to thirddomains “M1,” “M2,” and “M3” like the third preferred embodiment.Because the first to third domains “M1” to “M3” have the samecharacteristic as shown in FIG. 17 of the third preferred embodiment,additional description is omitted.

A positive liquid crystal (reference 80 of FIG. 17) is preferably usedwith a rubbing direction that is parallel to the common and pixelelectrodes 84 and 88. If a negative liquid crystal is used for thesecond preferred embodiment, a rubbing direction that is perpendicularto the common and pixel electrodes 84 and 88 is employed for the fourthpreferred embodiment.

Fifth Preferred Embodiment

FIG. 19 is a plan view illustrating a pixel region of the fifthpreferred embodiment. As shown in FIG. 19, except for male electrodes 77of a pixel electrode 76, the fifth preferred embodiment has the samestructure as the first preferred embodiment shown in FIG. 12. A pair ofmale electrodes 77 of the pixel electrode 76 protrude along a boundaryline “X” between first and second co-linear portions 62 a and 62 b of acommon electrode 62. Each male electrode 77 is perpendicular to thepixel electrode 76.

The male electrodes 77 enhance the distortion of electric fields shownin FIG. 13. In addition, the first and second electric field “E1” and“E2” (see FIG. 13) become stronger around the boundary line “X” becauseof the male electrodes 77. Therefore, first and second domains “M1” and“M2” shown in FIG. 13 are formed more stably.

In addition, as shown in FIG. 20, the male electrodes according to thefifth preferred embodiment can be applied to the structure of the secondpreferred embodiment shown in FIG. 15. Except for male electrodes 87 ofa pixel electrode 86, the sixth preferred embodiment has the samestructure as the second preferred embodiment shown in FIG. 15. The maleelectrodes 87 of FIG. 20 have the same role as the male electrodes 77 ofFIG. 19.

Sixth Preferred Embodiment

FIG. 21 is a plan view illustrating a pixel region of the sixthpreferred embodiment. As shown in FIG. 21, except for first and secondmale electrodes 65 and 79 of common and pixel electrodes 64 and 76, thesixth preferred embodiment has the same structure as the third preferredembodiment shown in FIG. 16. A pair of first male electrodes 65 of thecommon electrode 64 protrude along a second boundary line “X2,” whichdivides a pixel electrode 78 into first and second pixel sub-electrodes78 a and 78 b. Each first male electrode 65 is perpendicular to thecommon electrode 64. Whereas, a couple of second male electrodes 79 ofthe pixel electrode 78 are protruded along a first boundary line “X1,”which divides the common electrode 64 into first and second commonsub-electrodes 64 a and 64 b. Each second male electrode 79 isperpendicular to the pixel electrode 78. The first and second maleelectrodes 65 and 79 serve the same role as the male electrodes 77 ofFIG. 19, that is they enhance the distortion of electric fields.

In addition, as shown in FIG. 22, the male electrodes according to thesixth preferred embodiment can be applied to the structure of the fourthpreferred embodiment shown in FIG. 18. Except for first and second maleelectrodes 85 and 89 of pixel and common electrodes 88 and 84, the sixthpreferred embodiment has the same structure as the fourth preferredembodiment shown in FIG. 18. The first and second male electrodes 85 and89 of FIG. 22 have the same role as the first and second male electrodes65 and 79 of FIG. 21, that is to enhance distortion of electric fields.

Seventh Preferred Embodiment

FIG. 23 is a plan view illustrating a pixel region of the seventhpreferred embodiment. As shown, a plurality of common and pixelelectrodes 90 and 100 are alternately arranged with intervalstherebetween. The plurality of common electrodes 90 have an auxiliarycommon electrode 92, which is formed perpendicular to the commonelectrodes 90. Whereas, the plurality of pixel electrodes 100 have anauxiliary pixel electrode 102, which is formed perpendicular to thepixel electrodes 100. In other words, the auxiliary common electrode 92is parallel to a common line 60 and is integrally formed with theplurality of common electrodes 90. In addition, the auxiliary pixelelectrode 102 is parallel to the gate electrode 50 and is integrallyformed with the plurality of pixel electrodes 100.

Preferably, the auxiliary pixel electrode 102 is disposed along a firstboundary line “X1,” which sequentially divides the pixel electrodes 100into one-third and two-third portions. In addition, the auxiliary commonelectrode 92 is preferably disposed along a second boundary line “X2,”which sequentially divides the common electrodes 90 into two-third andone-third portions. That is to say, for the seventh preferredembodiment, first and second male electrodes 65 and 79 of the sixthpreferred embodiment shown in FIG. 21 are respectively connected withadjacent ones. Specifically, the first male electrodes 65 (see FIG. 21)are connected to form the auxiliary common electrode 92, whereas thesecond male electrodes 79 (see FIG. 21) are connected to form theauxiliary pixel electrode 102.

The check pattern-like common and pixel electrodes 90 and 102 improvedistortion and strength of electric fields between the common and pixelelectrodes 90 and 102 such that a faster response time is achieved. Inaddition, because a check pattern-like multi-domain is formed on thepixel region, a color dispersion property of the IPS-LCD device isimproved. That is to say, liquid crystal molecules are differentlyaligned for each domain such that the different domains compensate eachother to achieve a zero birefringence.

As previously explained, the first to seventh preferred embodimentsadopt a multi-domain, where different domains compensate for each other.To achieve the multi-domain, the first to seventh preferred embodimentsuses variously distorted electric fields such that liquid crystalmolecules are differently aligned in the various domains.

Eighth Preferred Embodiment

FIG. 24A is a partial expanded plan view illustrating an array substrate110 for an IPS-LCD device according to the eighth preferred embodiment.As shown, a gate line 50 is transversely formed on the array substrate110, and a data line 70 is formed perpendicular to the gate line 50. Ata crossing point between the gate and data lines 50 and 70, a gateelectrode 52 and a source electrode 72 are integrally formed with thegate and data lines 50 and 70, respectively. In addition, a drainelectrode 74 is formed spaced apart from the source electrode 72. Thegate, source, and drain electrodes 52, 72, and 74 are included in a thinfilm transistor “S”.

On a pixel region defined by the gate and data lines 50 and 70, a commonelectrode 120 and a pixel electrode 130 are alternately arranged. Thecommon electrode 120 includes a plurality of first transverse commonelectrodes 120 a, first to third perpendicular common electrodes 120 b,120 c, and 120 d, and second transverse common electrode 120 e, all ofwhich are bar-shaped. The plurality of first transverse commonelectrodes 120 a are spaced apart from each other and are parallel togate line 50, on a first pixel region “P1” (see FIG. 24B). The first andsecond perpendicular common electrodes 120 b and 120 c are also spacedapart from each other and are perpendicular to the gate line 50, alongthe first and second pixel regions “P1” and “P2” (see FIG. 24B). Thethird perpendicular common electrode 120 d is disposed on the secondpixel region “P2” (see FIG. 24B) and is parallel to the first and secondcommon electrodes 120 b and 120 c. The second transverse commonelectrode 120 e is perpendicular to the first and second commonelectrodes 120 b and 120 c and connects the first to third perpendicularcommon electrodes 120 b to 120 d.

The pixel electrode 130 includes a plurality of first transverse pixelelectrodes 130 a, first and second perpendicular pixel electrodes 130 band 130 c, and second transverse pixel electrode 130 d, all of which arepreferably bar-shaped. The plurality of first transverse pixelelectrodes 130 a are spaced apart from each other and are parallel tothe first transverse common electrodes 120 a. The first and secondperpendicular pixel electrodes 130 b and 130 c are spaced apart fromeach other and are parallel to the first perpendicular common electrode120 b. The second transverse pixel electrode 130 d connects the firstand second perpendicular pixel electrodes 130 b and 130 c on the secondpixel region “P2” (see FIG. 24B). The transverse common and pixelelectrodes 120 a and 130 a are alternately arranged with intervalstherebetween, whereas the perpendicular common electrode 120 b and firstand second perpendicular pixel electrodes 130 b and 130 c arealternately arranged with intervals therebetween. The plurality oftransverse pixel electrodes 130 a are preferably perpendicular to thefirst perpendicular pixel electrode 130 b and are directly connectedtherewith.

FIG. 24B shows an alignment characteristic of the above-mentioned arraysubstrate 110. As shown, the pixel region defined by the gate and datalines 50 and 70 is divided into first and second pixel regions “P1” and“P2” depending on the shape of the electrodes thereon. That is to say,the plurality of first transverse common and pixel electrodes 120 a and130 a are alternately arranged on the first pixel region. Whereas, thefirst to third perpendicular common electrodes 120 b to 120 d arealternately arranged with the first and second perpendicular pixelelectrodes 130 b and 130 c on the second pixel region “P2.” The firstperpendicular pixel electrode 130 b is disposed along the first andsecond pixel regions “P1” and “P2,” while the second perpendicular pixelelectrode 130 c is disposed only on the second pixel region “P2.” Thoughnot shown in FIG. 24A, an alignment layer is formed over the arraysubstrate 110. The alignment layer (not shown) preferably has first andsecond rubbing directions 150 a and 150 b, which are formed usingdifferent rubbing processes. To form the rubbing direction, a rubbingfabric is preferably used. A photo-alignment layer may be used as thealignment layer. Then, first and second liquid crystal portions 80 a and80 b are respectively aligned according to the first and second rubbingdirections 150 a and 150 b.

Preferably, the first liquid crystal portion 80 a is aligned accordingto the first rubbing direction 150 a such that long axes of molecules ofthe first liquid crystal portion 80 a are at an angle of 45 degrees withrespect to the first transverse pixel electrode 130 a. In addition, thesecond liquid crystal portion 80 b is aligned according to the secondrubbing direction 150 b such that long axes of molecules of the secondliquid crystal portion 80 b are at an angle of 45 degrees with respectto the first transverse pixel electrode 130 a. That is to say, the firstand second liquid crystal portions 80 a and 80 b are symmetricallyaligned by the first and second rubbing directions 150 a and 150 b,respectively. The symmetrical first and second pixel regions “P1” and“P2” compensate each other for zero birefringence such that a colorshift with respect to wide viewing angles is prevented. In an on stateof the IPS-LCD device, all the liquid crystal molecules are alignedperpendicular to the common and pixel electrodes 120 and 130. At thispoint, because the inventive IPS-LCD device has no bending portion,disclinations of a conventional IPS-LCD device shown in FIG. 10 do notoccur.

Returning to FIG. 24A, each of the first transverse common and pixelelectrodes 120 a and 130 a has a width “W1,” and adjacent transversecommon and pixel electrodes 120 a and 130 a are spaced apart with aninterval “W2” therebetween. For optimized operation of the IPS-LCDdevice using 5V as a driving voltage, the width “W1” and interval “W2”preferably have a ratio of 5:8 (W1:W2=5:8). Since the above-mentionedoptimization for the first pixel region “P1” of FIG. 24B is related to arelatively wider interval between the adjacent gate lines 50, theabove-mentioned optimized design is possible. However, optimization forthe second pixel region “P2” is more difficult than that of the firstpixel region “P1” because of a relatively narrower interval between theadjacent data lines 70.

The pixel electrode 130 is preferably made from a transparent conductivematerial, usually indium tin oxide (ITO), which has a hightransmittance. Meanwhile, the common electrode 120 is usually made ofthe same material as the gate line 50, but the transparent conductivematerial is preferably used for the common electrode 120 to achieve ahigher aperture ratio.

Now, with reference to FIGS. 25A, 25B, 26A, 26B, 27A and 27B, which aresequential cross-sectional views taken along first and second lines“I-I” and “II-II” of FIG. 24A, a fabricating method for theabove-mentioned IPS-LCD device is explained. At this point, the commonand pixel electrodes are made of the same transparent conductivematerial.

As shown in FIGS. 25A and 25B, the gate line 50 and gate electrode 52are integrally formed on the array substrate 110. To form the gate line50 and gate electrode 52, a first metal is deposited on the arraysubstrate 110 and patterned. The first metal is preferably selected froma group consisting of chromium (Cr), aluminum (Al); aluminum alloy (Alalloy), molybdenum (Mo), tantalum (Ta), tungsten (W), antimony (Sb), andan alloy thereof. Then, a gate-insulating layer, or a first insulatinglayer 160 is formed over the array substrate 110 such that the gate line50 and gate electrode 52 are covered. The gate-insulating layer ispreferably selected from an organic insulating material such asbenzocyclobutene (BCB) and acryl resin, or an inorganic insulatingmaterial such as silicon dioxide (SiO₂) and silicon nitride (SiN_(x)).On the gate-insulating layer 160, an amorphous silicon layer (a-Si:H)and a doped amorphous silicon layer (n+a-Si:H) are sequentiallydeposited and patterned to form an active layer 162 and an ohmic contactlayer 164. The active layer 162 and ohmic contact layer 164 have anisland shape. Thereafter, a second metal is deposited over the arraysubstrate 110 and patterned to form the data line 70, source electrode72, and drain electrode 74. The second metal is preferably the samematerial as the first metal.

Next, as shown in FIGS. 26A and 26B, the above-mentioned insulatingmaterial is deposited over the array substrate 110 such that a firstpassivation layer, or a second insulating layer 168 is formed on thesecond metal layer. The first passivation layer 168 is patterned to havea drain contact hole 168, which is disposed over the drain electrode 74.Then, a transparent conductive material is deposited and patterned onthe first passivation layer 168 to form the pixel electrode 130including the transverse pixel electrode 130 a and perpendicular pixelelectrode 130 b. The transparent conductive material is preferablyselected from a group consisting of indium tin oxide (ITO) and indiumzinc oxide (IZO). At this point, an outermost transverse pixel electrode130 a shown in right of FIG. 26B overlaps a portion of the gate line 50with the gate-insulating layer 160 and first passivation layer 166therebetween. The extended portion of the outermost transverse pixelelectrode 130 a serves as a first electrode of a storage capacitor(reference 280 of FIG. 27B). The pixel electrode 130 has the pluralityof transverse pixel electrodes 130 a, the first and second perpendicularpixel electrodes 130 b and 130 c, and the second transverse pixelelectrode 130 d (see FIG. 24A).

Next, as shown in FIGS. 27A and 27C, the insulating material isdeposited and patterned over the array substrate 110 such that a secondpassivation layer, or a third insulating layer 170 is formed to coverthe pixel electrode 130. Then, the transparent conductive material isdeposited and patterned on the second passivation layer 170 to form thecommon electrode 120 and common line 60. The common electrode 120includes the plurality of first transverse common electrodes 120 a,first to third perpendicular common electrodes 120 b to 120 d, andsecond transverse common electrode 120 e (see FIG. 24A). A portion ofthe common line 60 serves as a second electrode of the storage capacitor180. That is to say, portions of the outermost transverse pixelelectrode 130 a and common line 60 are used as the first and secondelectrodes for the storage capacitor 280.

Thereafter, a planar layer 200 is formed on the common electrode 130 andcommon line 60 such that the array substrate 110 has a plane surface. Onthe planar layer 200, an alignment layer 202 is formed. The alignmentlayer 202 has the first and second rubbing directions 150 a and 150 bshown in FIG. 24B. At this point, a sufficiently thick alignment layermay be used. In that case, the alignment layer 202 substitutes for theplanar layer 200 such that the planar layer 200 can be omitted.

It will be apparent to those skilled in the art that variousmodifications and variation can be made in the method of manufacturing athin film transistor of the present invention without departing from thespirit or scope of the invention. Thus, it is intended that the presentinvention cover the modifications and variations of this inventionprovided they come within the scope of the appended claims and theirequivalents.

1. An array substrate for an IPS-LCD device, comprising: a substrate; agate line on the substrate; a data line perpendicular to the gate line;a thin film transistor at a crossing portion between the gate and datalines; a common line parallel to the gate line, the common lineincluding first and second auxiliary common lines perpendicular to thecommon line; a plurality of common electrodes extending perpendicular tothe first and second auxiliary common lines; a plurality of pixelelectrodes arranged alternately with the plurality of common electrodes;an auxiliary common electrode perpendicularly contacting each of thecommon electrodes; and an auxiliary pixel electrode perpendicularlycontacting each of the pixel electrodes, wherein the auxiliary pixelelectrode is spaced apart from the auxiliary common electrodes, whereinthe plurality of common electrodes have portions that do not continueentirely across a pixel region, wherein the portions of the plurality ofcommon electrodes that do not continue entirely across the pixel regionand the auxiliary pixel electrode form a first virtual line parallel tothe data line, wherein each of the plurality of common electrodes isdivided into first and second common sub-electrodes by the first virtualline, wherein the plurality of pixel electrodes have portions that donot continue entirely across the pixel region, and wherein the portionsof the plurality of pixel electrodes that do not continue entirelyacross the pixel region and the auxiliary common electrode form a secondvirtual line parallel to the data line.